We can define an inbred individual as an individual whose parents are more closely related
to each other than two random individuals drawn from some reference population. [. . .]

1.6 Summarizing population structure

We defined inbreeding as having parents that are more closely related to each other than
two individuals drawn at random from some reference population. The question that natu-
rally arises is: Which reference population should we use? While I might not look inbred in
comparison to allele frequencies in the United Kingdom (UK), where I am from, my parents
certainly are not two individuals drawn at random from the world-wide population. If we
estimated my inbreeding coefficient F using allele frequencies within the UK, it would be
close to zero, but would likely be larger if we used world-wide frequencies. This is because
there is a somewhat lower level of expected heterozygosity within the UK than in the human
population across the world as a whole.

Wright (1943, 1951) developed a set of ‘F-statistics’ (also called ‘fixation indices’) that
formalize the idea of inbreeding with respect to different levels of population structure. He
defined F XY as the correlation between random gametes, drawn from the same level X,
relative to level Y.

[. . .] the reduction in heterozygosity within individuals compared to that expected in the
total population can be decomposed to the reduction in heterozygosity of individuals com-
pared to the subpopulation, and the reduction in heterozygosity from the total population
to that in the subpopulation.

Prompted by a troll post at Sailer's, I did a quick tally of the regional ancestries of Jeb's and G.W.'s great, great, great-grandparents (while I started with 3g-grandparents, I looked farther back wherever possible to identify any likely New England ancestry). The numbers I come up with:

New England: 10.125 / 32 = 31.64%

Mid-Atlantic: 11.375 / 32 = 35.55%

South: 7 / 32 = 21.88%

Germany: 2 / 32 = 6.25%

Britain: 1.5 / 32 = 4.69%

Less than a third of Jeb's ancestry actually traces back to New England. You can see the table of Bush ancestors I used here, and see to which region I assigned each of the the 3g-grandparents below the fold (in most cases I chose to count Maryland as Southern; but where Maryland ancestry was mixed with Pennsylvania ancestry I counted it as mid-Atlantic).

While the Bushes represent the very epitome of hated Yankee/Puritan for many anti-New England types, they in fact have twice as much non-New England as New England ancestry.

Vanishing American, in a longer post, which I highly recommend reading and which I'll probably write more about later, notes:

This whole notion of cultural DNA being passed on from long-ago departed former inhabitants of a place sounds a bit like the popular superstition that ghosts of long-past eras hang around their former home and ''possess'' the people who later inhabit their haunted territory. So if I understand it right, the WASPs and Puritans of old New England are now possessing the bodies of all the diversities who live in Boston and New Haven or Manchester, N.H., and maybe even those Somalis that live in Lewiston, Maine.

I found this observation amusingly apt, having just finished listening to an interview with Colin Woodard in which the following exchange occurs (around 39 minutes into this podcast):

Host: One of the big fears in many countries is how immigration will change the very nature of a city or a state or a place and what's interesting from what you're saying is actually you can be a little more relaxed about that because there's something almost secretive, deep-rooted, almost magical, you can't quite explain it logically that lives on generation to generation, that if you have a sensible immigration policy actually the people who come will be pulled into that story as well, because as you've said before when you go back to look at some of these communities the people for example in New York who trace their roots back to being Dutch is minimal but something from that settlement still affects New Yorkers.

Woodard: You are correct, in that in theory in any country or place in the world if one moves there you would assimilate maybe you personally wouldn't fully successfully do it because you'll always be a foreigner maybe in your own mind or can't master the language completely. But your children will and your grandchildren almost certainly will, if there aren't cultural impediments to being assimilated or allowed to assimilate.

Woodard's mother has a common name, and I was unable to immediately identify her parents or birth place. I did easily identify the ancestor's of Woodard's father going back a few generations.

While Colin Woodard describes himself as a native of Maine, his father (who has an MA in Creative Writing from Syracuse and now teaches introductory English at the University of Maine Augusta) was born in Los Angeles, and his father's parents were born in Montana (the mother being of 100% Irish Catholic ancestry, as far as I can tell).

Of his father's great-grandparents:

Only three were born in America (according to census documents, one was born in Michigan, with parents also born in Michigan, and two were born in New York, with parents also born in New York).

Four were born in Ireland (and evidently Catholic).

One was born in Quebec (with, going by names, a French Canadian father and Irish Catholic mother).

So Colin Woodard's father is something like 9/16 Irish Catholic, 1/16 French Canadian, and no more than 3/8 colonial American (and it's unlikely the entirety of the American ancestry traces back to New England).

After writing the above, I checked one last time for any information on Colin's mother ancestry, and came across this article from Woodard himself. In addition to confirming parts of his paternal ancestry:

My Irish-Catholic great-grandparents worked the iron and copper mines of the interior West, and their children grew up to be Far Westerners. My great-great-great grandmother’s family fled from the same part of Ireland as their future cousins-in-law, but the mines where they found work happened to be in Quebec, so their descendants grew up speaking French and traveling on aboriginal snowshoes.

Woodard mentions:

Life in North America has been immeasurably enriched by the many cultures and people who settled there. I personally celebrate the continent’s diversity, but I also know that my great-grandfather’s people in western Iowa -- Lutheran farmers from the island of Funen in Denmark -- assimilated into the dominant culture of the Midlands (think, for now, “Midwest”), even as they contributed to its evolution.

JayMan supports the above JayMan assertion by linking to another JayMan comment, which sees JayMan copy-and-pasting from Wikipedia a table of inbreeding coefficients by degree of relationship, and asserting the table:

…demonstrates why “ethnic genetic interests” do not exist.

Let that sink in. "HBD" hobbyist JayMan sees coefficients of relationship near zero, and asserts (without being fully aware of what he's asserting) that this means I don't share any particular genetic relatedness with my third cousin relative to a tribesman from New Guinea or a triracial from Jamaica.

This is of course not what an inbreeding coefficient near zero indicates:

The solution to the problem posed in Figure 5.1 will be easy if we can calculate the
inbreeding coefficient f H of individual H. The inbreeding coefficient of an individual is
the probability that the two gene copies present at a locus in that individual are identical
by descent, relative to an appropriate base population. Two genes are identical by descent
if, and only if, they are descended from the same individual gene copy. Now of course
we must stop somewhere as we trace back the ancestry of the two genes. Otherwise
any two gene copies would be certain of being identical by descent, provided that life
has a monophyletic origin. The function of the base population is to set the context of
the problem. In the base population, all gene copies are assumed not to be identical by
descent. [Joe Felsenstein. Theoretical Evolutionary Genetics.]

I'm not much more closely related to my third cousin than to a random member of the approximately-random-breeding population from which we both spring. I am genetically markedly more similar to my third cousin (and any other Northwestern European) than I am to someone like JayMan. This is the essence of "ethnic genetic interests".

From Henry Harpending's appendix to Frank Salter's book:

The coefficient of kinship between two diploid organisms describes their overall
genetic similarity to each other relative to some base population. For example, kinship between parent and offspring of 1/4 describes gene sharing in excess of random sharing in a random mating population. In a subdivided population the statistic Fst describes gene sharing within subdivisions in the same way. Since Fst among human populations on a world scale is reliably 10 to 15%, kinship between two individuals of the same human population is equivalent to kinship between grandparent and grandchild or between half siblings. The widespread assertion that this is small and insignificant should be reexamined.

Note also that debates about group selection ultimately have no bearing on the reality of ethnic genetic interests, the existence of which is inarguable. When people from the population I belong to are replaced with members of genetically distant populations, this represents a loss of inclusive fitness for me, and one I see no reason to tolerate, irrespective of how strongly selection has operated at the level of groups in the past.

New preprint confirming what those of us who were paying attention were able to infer yearsago:

We generated genome-wide data from 69 Europeans who lived between 8,000-3,000 years ago by enriching ancient DNA libraries for a target set of almost four hundred thousand polymorphisms. Enrichment of these positions decreases the sequencing required for genome-wide ancient DNA analysis by a median of around 250-fold, allowing us to study an order of magnitude more individuals than previous studies and to obtain new insights about the past. We show that the populations of western and far eastern Europe followed opposite trajectories between 8,000-5,000 years ago. At the beginning of the Neolithic period in Europe, ~8,000-7,000 years ago, closely related groups of early farmers appeared in Germany, Hungary, and Spain, different from indigenous hunter-gatherers, whereas Russia was inhabited by a distinctive population of hunter-gatherers with high affinity to a ~24,000 year old Siberian6. By ~6,000-5,000 years ago, a resurgence of hunter-gatherer ancestry had occurred throughout much of Europe, but in Russia, the Yamnaya steppe herders of this time were descended not only from the preceding eastern European hunter-gatherers, but from a population of Near Eastern ancestry. Western and Eastern Europe came into contact ~4,500 years ago, as the Late Neolithic Corded Ware people from Germany traced ~3/4 of their ancestry to the Yamnaya, documenting a massive migration into the heartland of Europe from its eastern periphery. This steppe ancestry persisted in all sampled central Europeans until at least ~3,000 years ago, and is ubiquitous in present-day Europeans. These results provide support for the theory of a steppe origin of at least some of the Indo-European languages of Europe. [. . .]

R1a and R1b are the most common haplogroups in many
European populations today 18,19 , and our results suggest that they spread into Europe from the
East after 3,000 BCE. Two hunter-gatherers from Russia included in our study belonged to
R1a (Karelia) and R1b (Samara), the earliest documented ancient samples of either
haplogroup discovered to date. These two hunter-gatherers did not belong to the derived
lineages M417 within R1a and M269 within R1b that are predominant in Europeans
today 18,19 , but all 7 Yamnaya males did belong to the M269 subclade 18 of haplogroup R1b.